U.S. patent application number 17/104004 was filed with the patent office on 2021-03-18 for computer-assisted surgery system and method for orienting a knee implant.
The applicant listed for this patent is ORTHOSOFT ULC. Invention is credited to Karine DUVAL, Bruno FALARDEAU, Catherine LEVEILLE, Benoit PELLETIER.
Application Number | 20210077121 17/104004 |
Document ID | / |
Family ID | 1000005240285 |
Filed Date | 2021-03-18 |
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United States Patent
Application |
20210077121 |
Kind Code |
A1 |
LEVEILLE; Catherine ; et
al. |
March 18, 2021 |
COMPUTER-ASSISTED SURGERY SYSTEM AND METHOD FOR ORIENTING A KNEE
IMPLANT
Abstract
A reference jig comprises a base adapted to be secured to a
distal end of a bone. An adjustment mechanism has a bracket, one or
more rotational joints operatively mounting the bracket to the
base, whereby the bracket is rotatable in two or more rotational
degrees of freedom relative to the base, and one or more
translational joints. A landmark alignment unit is operatively
connectable to the bracket by the at least one translational joint,
the landmark alignment unit having a bone alignment component
configured to be aligned with at least one bone landmark.
Inventors: |
LEVEILLE; Catherine;
(Montreal, CA) ; PELLETIER; Benoit; (Montreal,
CA) ; FALARDEAU; Bruno; (Verdun, CA) ; DUVAL;
Karine; (Montreal, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ORTHOSOFT ULC |
Montreal |
|
CA |
|
|
Family ID: |
1000005240285 |
Appl. No.: |
17/104004 |
Filed: |
November 25, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
16013282 |
Jun 20, 2018 |
10874405 |
|
|
17104004 |
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62522398 |
Jun 20, 2017 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 17/155
20130101 |
International
Class: |
A61B 17/15 20060101
A61B017/15 |
Claims
1. A method for positioning a cut guide on a femur, comprising:
connecting a portion of a reference jig to a distal end of a femur;
orienting the reference jig to be aligned with a posterior condylar
plane of the femur and/or a transepicondylar line of the femur to
obtain a femoral coordinate system including at least one femoral
landmark; and positioning a cut guide relative to the femur using
the at least one femoral landmark as a reference.
2. The method according to claim 1, wherein connecting the portion
of the reference jig includes inserting a spike of the reference
jig in the femur.
3. The method according to claim 2, wherein inserting the spike of
the reference jig in the femur includes inserting the spike at an
entry point of a mechanical axis of the femur.
4. The method according to claim 1, wherein orienting the reference
jig includes orienting the reference jig to abut distal aspects of
the bone on both sides of the portion of the reference jig.
5. The method according to claim 4, wherein orienting the reference
jig to abut the distal aspects of the femur includes rotating the
reference jig about an axis generally parallel to an
anterior-posterior axis of the femur.
6. The method according to claim 4, wherein orienting the reference
jig to abut the distal aspects of the femur includes rotating the
reference jig about an axis generally parallel to a medio-lateral
axis of the femur.
7. The method according to claim 1, wherein orienting the reference
jig includes abutting the reference jig against the posterior
condylar plane of the femur.
8. The method according to claim 7, wherein abutting the reference
jig against the posterior condylar plane of the femur includes
translating a condylar abutment of the reference jig against the
posterior condyles.
9. The method according to claim 1, wherein orienting the reference
jig includes positioning a jaw of the reference jig on the femur
such that ends of the jaw pass through the transepicondylar line of
the femur.
10. The method according to claim 1, further including securing the
at least one femoral landmark to the femur relative to the
reference jig, the at least one landmark being at least one guide
pin.
11. The method according to claim 10, wherein positioning the cut
guide relative to the femur includes positioning the cut guide
using the at least one guide pin.
12. The method according to claim 1, including moving the femur
with the reference jig aligned with the posterior condylar plane of
the femur and/or the transepicondylar line of the femur, such that
a tracking of the moving defines a center of rotation of the femur
relative to the femoral coordinate system.
13. The method according to claim 1, including resecting the femur
using the cut guide.
14. The method according to claim 13, wherein resecting the femur
using the cut guide include defining a distal cut.
15. The method according to claim 14, including securing a pin
having a ball head at an entry point of the mechanical axis of the
femur.
16. The method according to claim 15, including attaching another
cut guide to the ball head to form a rotational joint.
17. The method according to claim 16, including orienting the other
cut guide relative to the femoral coordinate system.
18. The method according to claim 17, wherein orienting the other
cut guide include abutting the other cut guide against posterior
condyles.
19. The method according to claim 18, including resecting the femur
using the other cut guide to define a posterior cut.
20. A system for validating a distal cut of a femur comprising: a
processor unit; and a non-transitory computer-readable memory
communicatively coupled to the processing unit and comprising
computer-readable program instructions executable by the processing
unit for: tracking a femoral coordinate system with a first
inertial sensor unit of a computer-assisted surgery (CAS) system
secured to the femur, receiving readings of a second inertial
sensor unit of the computer-assisted surgery (CAS) as supported by
a guide coplanar against the distal cut, determining an orientation
of a plane of the distal cut in the femoral coordinate system, and
validating the orientation with a planned orientation of the distal
cut.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is a continuation of U.S. patent
application Ser. No. 16/013,282, filed on Jun. 20, 2018 and which
claims the priority of U.S. Patent Application No. 62/522,398,
filed on Jun. 20, 2017 and incorporated herein by reference.
FIELD OF THE APPLICATION
[0002] The present application relates to computer-assisted surgery
systems for instance using inertial sensors and, more particularly,
to instrumentation used for guiding bone alterations in knee
arthroplasty for the subsequent placement of a femoral and/or
tibial implant.
BACKGROUND OF THE ART
[0003] Tracking of surgical instruments or tools is an integral
part of computer-assisted surgery (hereinafter CAS). The tools are
tracked for position (x,y,z coordinates) and/or orientation (phi,
theta, rho angles) in such a way that information pertaining to
bodily parts is obtained. The information is then used in various
interventions (e.g., orthopedic surgery, neurological surgery) with
respect to the body, such as bone alterations, implant positioning,
incisions and the like during surgery. In particular, in the
context of knee arthroplasty, an operator may require information
relating to an orientation of cut blocks and cut guide relative to
the distal end of the femur, to ensure adequate implant positioning
to avoid or minimize any varus or valgus.
[0004] Inertial sensors such as accelerometers are commonly used
for the tracking of surgical instruments. Some inertial sensors may
be limited to outputting orientation tracking along two degrees of
freedom (DOF) only, and/or an output of some inertial sensors may
be without positional tracking. Accordingly, specific steps must be
taken during surgery to provide the operator with the necessary
navigation parameters in spite of the inherent two DOF limit or
orientation-only limitation of some inertial sensors.
SUMMARY OF THE APPLICATION
[0005] It is therefore an aim of the present application to provide
a novel method for performing alterations to a distal end of a
femur in knee arthroplasty.
[0006] Therefore, in accordance with a first embodiment of the
present disclosure, there is provided a reference jig comprising: a
base adapted to be secured to a distal end of a bone; an adjustment
mechanism having a bracket, at least one rotational joint
operatively mounting the bracket to the base, whereby the bracket
is rotatable in at least two rotational degrees of freedom relative
to the base, and at least one translational joint; and a landmark
alignment unit operatively connectable to the bracket by the at
least one translational joint, the landmark alignment unit having a
bone alignment component configured to be aligned with at least one
bone landmark.
[0007] Further in accordance with the first embodiment, the bracket
has for instance at least one abutment surface adapted to abut
distal aspects of the bone.
[0008] Still further in accordance with the first embodiment, the
bone alignment component is for instance a posterior abutment
adapted to abut posterior aspects of the bone.
[0009] Still further in accordance with the first embodiment, the
bracket has for instance at least one abutment surface adapted to
abut distal aspects of the bone, a plane of the at least one
abutment surface being perpendicular to a plane of the posterior
abutment.
[0010] Still further in accordance with the first embodiment, the
posterior abutment is for instance a condylar abutment adapted to
abut against posterior aspects of condyles.
[0011] Still further in accordance with the first embodiment, a
first rotational axis of the at least one rotational joint is for
instance generally parallel to an anterior-posterior axis of the
bone.
[0012] Still further in accordance with the first embodiment, a
second rotational axis of the at least one rotational joint is for
instance generally parallel to a medio-lateral axis of the
bone.
[0013] Still further in accordance with the first embodiment, the
bone alignment component has for instance a jaw supporting a pair
of ends separated from one another for positioning the bone
between.
[0014] Still further in accordance with the first embodiment, the
bracket has for instance at least one abutment surface adapted to
abut distal aspects of the bone, a plane of the at least one
abutment surface being parallel to a line passing through the ends
of the jaw.
[0015] Still further in accordance with the first embodiment, the
jaw is for instance a transepicondylar line jaw.
[0016] Still further in accordance with the first embodiment, the
at least one translational joint includes for instance a pair of
slots in the bracket, and a pair of rails slidingly received in the
slots and connected to the bone alignment component.
[0017] Still further in accordance with the first embodiment, an
inertial sensor unit is for instance mounted to the base.
[0018] Still further in accordance with the first embodiment, the
base has for instance a receptacle for releasably receiving the
internal sensor unit in a known geometric relation.
[0019] Still further in accordance with the first embodiment, the
base has for instance a spike adapted to be received in the
bone.
[0020] In accordance with a second embodiment of the present
disclosure, there is provided an assembly comprising: the reference
jig as described above; a cut block having a cut slot releasably
connected to the reference jig so as to be displaceable with the
bracket in the at least two rotational degrees of freedom; at least
one inertial sensor unit connected to at least one of the reference
jig and the cut block to track a variation of orientation of the
cut slot relative to the bone.
[0021] Still further in accordance with the second embodiment, one
said inertial sensor unit is for instance connected to the
reference jig, and another said inertial sensor unit connected to
the cut block.
[0022] In accordance with a third embodiment of the present
disclosure, there is provided a cut guide comprising: a bone anchor
adapted to be received in a bone and project beyond a resected bone
plane; a base having defining an underside with a sliding plane
adapted to be laid against the resected bone plane; at least one
rotational joint operatively mounting the bone anchor to the base,
whereby the bracket is rotatable in a rotational degree of freedom
while sliding on the resected bone plane, and an inertial sensor
unit mounted to the base for determining an orientation of the
resected bone plane.
[0023] Further in accordance with the third embodiment, at least
one translational joint and a landmark alignment unit are for
instance operatively connectable to the bracket by the at least one
translational joint, the bone landmark alignment unit having a bone
alignment component configured to be aligned with at least one bone
landmark.
[0024] Still further in accordance with the third embodiment, the
bone alignment component is for instance a posterior abutment
adapted to abut posterior aspects of the bone.
[0025] Still further in accordance with the third embodiment, the
posterior abutment is for instance a condylar abutment adapted to
abut against posterior aspects of condyles.
[0026] Still further in accordance with the third embodiment, the
at least one translational joint includes for instance a slot in
the base, and a ball at the bone anchor, the ball and slot forming
the at least one rotational joint and the at least one rotational
joint.
[0027] Still further in accordance with the third embodiment, a
bracket is for instance provided, a translational joint is for
instance between the bracket and the base for translational
movement of the bracket relative to the base in a direction
generally parallel to the resected bone plane, and a sizing boom is
for instance on the bracket.
[0028] Still further in accordance with the third embodiment, a
scale is for instance formed between the bracket and the base at
the translational joint.
[0029] In accordance with a fourth embodiment of the present
disclosure, there is provided a method for creating a femoral
coordinate system comprising: securing a reference jig at a distal
end of a femur, the reference jig supporting an inertial sensor
unit programmed with a known geometrical relation with respect to a
femoral landmark; orienting the reference jig to be in aligned with
one of a posterior condylar plane of the femur and a
transepicondylar line of the femur; recording movements of the
femur for tracking by the inertial sensor unit; and obtaining a
femoral coordinate system defined by a femoral axis including the
femoral landmark, a center of rotation of the femur and an
alignment with the one of the posterior condylar plane of the femur
and of the transepicondylar line of the femur.
[0030] In accordance with a fifth embodiment of the present
disclosure, there is provided a system for validating a distal cut
of a femur comprising: a processor unit; and a non-transitory
computer-readable memory communicatively coupled to the processing
unit and comprising computer-readable program instructions
executable by the processing unit for: tracking a femoral
coordinate system with a first inertial sensor unit of a
computer-assisted surgery (CAS) system secured to the femur,
receiving readings of a second inertial sensor unit of the
computer-assisted surgery (CAS) as supported by a guide coplanar
against the distal cut, determining an orientation of a plane of
the distal cut in the femoral coordinate system, and validating the
orientation with a planned orientation of the distal cut.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a flow chart of a method for performing
alterations to a distal end of a femur in knee arthroplasty in
accordance with the present disclosure, using inertial sensors of a
computer-assisted surgery system;
[0032] FIG. 2 is a perspective view of a knee reference jig in
accordance with a first embodiment of the present disclosure, as
mounted to a distal femur with alignment with a condylar plane;
[0033] FIG. 3 is a perspective view of the knee reference jig of
FIG. 2, as detached from the femur;
[0034] FIG. 4 is another perspective view of the knee reference jig
of FIG. 2, as detached from the femur;
[0035] FIG. 5 is a perspective view of a condylar abutment of the
knee reference jig of Fig.;
[0036] FIG. 6 is a perspective view of a knee reference jig in
accordance with a second embodiment of the present disclosure, as
mounted to a distal femur, for transepicondylar line alignment
[0037] FIG. 7 is an assembly view of the knee reference jig of FIG.
6;
[0038] FIG. 8 is a perspective view of jaw of the knee reference
jig of FIG. 6;
[0039] FIG. 9 is a perspective view of a cut block in accordance
with the present disclosure, as mounted to the distal femur after
distal cut;
[0040] FIG. 10 is a perspective view of a cutting guide in
accordance with another embodiment of the present disclosure, as
validating a distal cut;
[0041] FIG. 11 is a perspective view of the cutting guide of FIG.
9, as detached from the femur;
[0042] FIG. 12 is another perspective view of the cutting guide of
FIG. 9, as detached from the femur; and
[0043] FIG. 13 is a perspective view of the cutting guide of FIG.
12, with a sizing bracket.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] Referring to FIG. 1, a method for performing alterations to
a distal end of a femur in knee arthroplasty, using for instance
inertial sensors of a computer-assisted surgery (CAS) system, is
shown at 10. The alterations may be cuts and holes for a femoral
knee implant to then be implanted at the distal end of the femur,
at a position and orientation decided by the operator, through
guidance of a CAS system in making bone alterations for receiving
the femoral knee implant. As per convention, the distal end of the
femur is the knee end of the femur, whereas the proximal end of the
femur is the femoral head end of the femur. The method 10 guides
the operator in performing the alterations on the distal end of the
femur. The method is described with reference to 11-18 of FIG. 1,
all representing steps of groups of steps, and with reference to
hardware and electronic components, shown starting at FIG. 2.
[0045] According to 11, a knee reference jig is attached to the
distal end of the femur. The knee reference jig may be as shown at
20 in FIGS. 2-5, or as shown as 30 in FIGS. 6-8, as detailed
hereinafter. The knee reference jig may be attached to be located
at a mechanical axis entry point of the distal end of the femur. A
pin may then serve as a joint for movement of the knee reference
jig 20 or 30 relative to the distal end of the femur. Other types
of knee reference jigs may also be used, with the knee reference
jigs 20 and 30 provided as examples. The knee reference jig 20 or
30 are used in such a way that the tools during the procedure are
consistently aligned with selected bone landmarks throughout the
procedure.
[0046] According to 12, an orientation of the knee reference jig
20/30 is set relative to the distal end of the femur. In other
words, the knee reference jig 20/30 has its position and
orientation fixed relative to the distal end of the femur, using
for example screw(s) to pin the jigs 20/30 to the bone once an
appropriate orientation is attained. The position of the knee
reference jig 20/30 may be defined as being at the mechanical axis
entry point, whereas its orientation can be set by abutments with
bone landmarks. In an embodiment, the knee reference jig may be
aligned with Whiteside's line. In another embodiment, the knee
reference jig 20 is aligned with the condyles, and more
particularly with the posterior plane of the condyles. The
posterior plane may be perpendicular to the plane in which lie the
distal-most points of the condyles, and may include the
posterior-most points of the condyles. In another embodiment, the
knee reference jig 30 is aligned with the transepicondylar axis,
i.e., the line between the most medial and lateral prominences of
the epicondyles.
[0047] According to 13, a femoral coordinate system is created
(also known as femoral frame of reference). The femoral coordinate
system is a virtual coordinate system, i.e., virtually tracked,
that is in register with physical landmarks of the femur. The
virtual femoral coordinate system is therefore representative of
the femur, with hardware components then tracked as a function of
the femoral coordinate system to determine their orientation. To
create the femoral coordinate system, the devices used in the
procedure, such as the jigs 20 and 30, are equipped with an
inertial sensor unit B1 so as to be in a fixed relation with the
femur, and movements of the femur are made while recorded by the
fixed inertial sensor unit B1. The inertial sensor unit B1 is an
electronic component of the computer-assisted surgery (CAS) system,
and outputs a signal representative of an orientation of the unit
B1. The inertial sensor unit B1 and/or the CAS system may be
programmed with geometrical data and preset virtual orientations,
for the output of the inertial sensor unit B1 to be representative
of an arrangement between the inertial sensor unit B1 and the
femur, as described below.
[0048] Still in 13, the femoral coordinate system may include a
mechanical axis of the femur, as well as an orientation of the jigs
20/30 relative to the desired landmark (e.g., Whiteside's line,
posterior plane of the condyles, transepicondylar axis, etc). The
mechanical axis of the femur may be determined from the movements
that are used by the CAS system to identify a position of the
center of rotation of the femoral head, and the programmed data of
the geometrical relation of the inertial sensor unit B1 on the knee
reference jig 20/30, enabling the CAS system to determine the entry
point of the mechanical axis at the distal femur. For example, the
inertial sensor unit B1 incorporates at least one accelerometer and
at least one gyroscope and employs the method as described in U.S.
Pat. No. 9,901,405, incorporated herein by reference.
[0049] According to 14, a cut block is navigated. Examples of cut
block navigations are for instance described in U.S. patent
application Ser. No. 13/035,264, and in U.S. Pat. No. 8,718,820,
both incorporated herein by reference. The cut block, for example
shown in one possible configuration as 40 in FIG. 9, is attached to
the knee reference jig 20/30. The cut block 40 is "navigated",
i.e., its orientation in the femoral coordinate system is tracked
via the inertial sensor unit B1 and another inertial sensor unit B2
integrally connected to the cut block 40, as orientation
adjustments via the knee reference jig 20/30. According to an
embodiment, the cut block 40 may be displaced in two rotational
degrees of freedom (DOF) with respect to a base of the knee
reference jig 20/30, one of the rotational DOFs being
representative of an anterior-posterior axis of the femur for
varus/valgus adjustment, and the other of the rotational DOFs being
generally aligned with a medio-lateral axis of the femur, for
flexion/extension adjustment. Once a desired orientation is reached
for a plane of the cut block 40, the cut block 40 may be pinned to
the femur, for the distal cut to be made. The plane of the cut
block 40 may be that of the cut slot of the cut block 40 adapted to
receive a saw blade and may consequently correspond to the eventual
distal cut.
[0050] The cut block 40 may have another inertial sensor unit, B2,
secured to it, with the geometrical relation between the cut block
40 and the inertial sensor unit B2 being programmed in the inertial
sensor unit B2, for the output of the inertial sensor unit B2 to be
representative of the plane of the cut block 40. In such an
arrangement, the inertial sensor units B1 and B2 are paired, for
the inertial sensor unit B1 to track the femoral frame of reference
while the inertial sensor unit B2 tracks the orientation
adjustments of the cut block 40 relative to the femur. However, in
another embodiment, it is contemplated to use a single inertial
sensor unit, as described hereinafter. Moreover, the femoral
coordinate system may be transferred to the inertial sensor unit B2
of the cut block 40 when the latter is fixed to the bone, for this
inertial sensor unit B2 to become the main tracking reference of
the CAS system tracking the femur via the femoral coordinate
system, as the reference jig 20/30 and inertial sensor unit B1 may
be detached from the femur for the distal cut to be effected, while
the cut block 40 remains attached to the femur.
[0051] According to 15, the distal cut is performed, using the cut
block 40. To perform the distal cut, the knee reference jig 20/30
may be removed from attachment to the femur. Any appropriate tool
may be used for the distal cut, such as flat surgical saw blades.
The distal cut is therefore oriented as desired by the preceding
actions from the operator, including the orientation aligned with
the Whiteside's line, posterior plane of the condyles, and/or
transepicondylar axis, as desired.
[0052] According to 16, the distal cut may be validated. A knee
cutting guide 50 as in FIGS. 10-13 may be used for the validation,
with an inertial sensor unit B3 thereon. This knee cutting guide 50
may be dedicated to navigating the distal cut plane, or may
supplementally be used for other functions, including planning the
anterior cut, sizing the implant, navigating the pin holes, as
described herein. For instance, the inertial sensor unit B3 may be
in communication with the inertial sensor unit B2 on the cut block
40, for the readings of the inertial sensor unit B3 to be as a
function of the femoral coordinate system tracked by the inertial
sensor unit B2. The inertial sensor unit B3 may be the inertial
sensor unit B1, programmed to perform the operations related to the
knee cutting guide 50, or may be another inertial sensor unit B3.
The inertial sensor units B1, B2 and B3 may in some instance be the
same and transferred via dead reckoning to preserve their reference
to the virtual femoral coordinate system.
[0053] The knee cutting guide 50 is laid flat on the distal cut,
and is therefore constrained from rotating in one rotational DOF.
The planar movements of the knee cutting guide 50 along the distal
cut allow a determination of the orientation of the plane of the
distal cut relative to the femoral coordinate system, and hence its
validation as it may be compared to a planned orientation (i.e., as
per the preceding steps). If the orientation of the distal cut must
be corrected, an orientation of the cut block 40 may be adjusted
via the inertial sensor unit B2, with a repeat of 14, 15 and 16,
for example. This may require the reinstallation of the reference
jig 20/30.
[0054] According to 17, the cut guide 50 is navigated, i.e., its
position and orientation relative to the femoral coordinate system
is selected based on its tracking, for the operator to determine
the orientation of addition femoral alterations, such as pin
placement, and various planar cuts, such as anterior cut, posterior
cut, posterior chamfer and/or anterior chamfer, as a function of
the implant that will be used. The cut guide 50 may be connected to
a pin A with ball head (shown throughout FIGS. 9-13) located at the
mechanical axis entry point, and forming a joint with the cut guide
50, allowing its movement. Sizing data may also be obtained. As the
femoral coordinate system incorporates known landmarks, such as
Whiteside's line, posterior plane of the condyles, and/or
transepicondylar axis, etc, the operator can plan the additional
femoral alterations by placing the cut guide 50 as a function of
the known landmarks. The cut guide 50 may serve to place a pair of
pins that will be used as landmarks for the placement of a femoral
finishing guide, by which other planes may be cut.
[0055] According to 18, these additional alterations are performed,
for the implant to be implanted. In an embodiment, the additional
alterations include the placement of pin landmarks for a femoral
finishing guide to be placed on the distal cut to perform
additional cuts, such as the cuts defining the anterior condyle
plane, the posterior condyle plane, the posterior chamfer and the
anterior chamfer.
[0056] Referring to FIGS. 2-5, the knee reference jig 20 is shown
in greater detail. The knee reference jig 20 is configured to
orient itself with the condyles (a.k.a., posterior referencing),
and is therefore used if the operator selects condylar alignment.
The jig 20 has a base 21 that defines the structure of the jig 20,
as the base 21 supports other components of the jig 20. A spike 22
or pin projects from the base 21, and is sized so as to be received
in a hole drilled in the distal femur at the mechanical axis entry
point. In an embodiment, the spike 22 may be an integral part of
and/or immovable with respect to the base 21. Therefore, when the
spike 22 is in the drilled hole, the jig 20 is at the mechanical
axis entry point. The base 21 has an abutment plane, herein shown
as a pair of abutment surfaces 23, for the distal aspects of the
condyles. A single abutment surface 23 may also be present, for
instance large enough to contact both condyles. The abutment
surfaces 23 abut against the distal surfaces (a.k.a., aspects) of
the condyles (i.e., medial and lateral condyles) when the spike 22
is received in the drilled hole. The base 21 also has a receptacle
24, for receiving the inertial sensor unit B1. The receptacle 24 is
shaped for receiving the inertial sensor unit B1, such that any
preset virtual orientation or like calibration data programmed into
the inertial sensor unit B1 is aligned with physical parts of the
jig 20, such as the abutment plane of the abutment surface(s) 23
and the spike 22.
[0057] An adjustment mechanism 25 is also operatively connected to
the base 21, by a pair of rotation joints aligned with axes R1 and
R2. The adjustment mechanism 25 has pivots 25A and 25B by which
bracket 25C can rotate relative to the base 21. The cut block 40
may be releasably attached to the jig 20 to the bracket 25C for
concurrent rotation with it. The other pivot 25B may be present as
well, to form a second rotational joint relative to the base 21.
The cut block 40 may be connected to the adjustment mechanism in
other ways as well, including onto slots 27 or rails 28. The
adjustment mechanism 25 has a pair of knobs 26 (concurrently
referred to as 26, but shown as 26A and 26B), the knobs 26
operating rotational joints featuring the pivots 25A and 25B,
respectively aligned with the anterior-posterior (AP) axis (knob
26A) and with the medio-lateral (ML) axis (knob 26B) when the jig
20 is attached to the femur in the manner described above. The
rotational joints may be of the self-locking type, in that they
hold the orientation to which they are adjusted. The bracket 25C is
therefore displaceable in two rotational DOFs relative to the base
21. The knobs 26 allow minute or micro orientation adjustments. The
base 21 may further define a pair of parallel slots 27 for
slidingly receiving the rails 28, in a translational DOF. A
landmark alignment unit is provided, as a condylar abutment 29
supported by the rails, such that the condylar abutment 29 may be
brought closer or further to the base 21. The condylar abutment 29
defines a condylar plane, configured to come into contact with
posterior aspects of the medial and lateral condyles. Hence a
surface of the condylar abutment 29 serves as a bone alignment
component. According to an embodiment, the condylar plane of the
condylar abutment 29 and the abutment plane of the abutment
surface(s) 23 are perpendicular to one another. The abutment
surface(s) 23, the bracket 25C, the rails 28 and the condylar
abutment 29 may all rotate concurrently relative to the base 21,
and the rotations may be fine-tuned by the knobs 26A and 26B, about
the AP axis and the ML axis, respectively.
[0058] Securing the knee reference jig 20 to the distal femur
according to 11 of FIG. 1 entails inserting the spike 22 in the
hole drilled at the mechanical axis entry point. In an embodiment,
the jig 20 is manually oriented such that the condylar plane of the
condylar abutment 29 contacts the posterior aspects of the
condyles. The base 21 may then be driven into the hole of the femur
20, with the penetration adjusted until the abutment plane of the
base 21 is against at least one of the distal aspects of the
condyles. The depth of penetration may be adjusted to allow some
play resulting in the abutment against the medial condyle and the
lateral condyle. Alternatively or additionally, the knob 26A may be
rotated to cause an adjustment of the orientation of the abutment
plane about the anterior-posterior axis relative to the base 21 and
bone. Likewise, the knob 26B may be rotated to cause an adjustment
of the orientation of the abutment plane about the medio-lateral
axis relative to the base 21 and bone. Setting the orientation as
in 12 of FIG. 1 may require rotating the base 21 on itself, i.e.,
relative to the spike 22, and translating the condylar abutment 29
until the condylar abutment 29 comes into contact with the
posterior aspects of both the medial and lateral condyles. However,
in one embodiment, the rotation of the base 21 may not be required
as it was performed initially before the base 21 was driven into
the femur. The knee reference jig 20 is thus oriented with the
posterior plane of the condyles.
[0059] The femoral coordinate system may be created by the
appropriate kinematics as described in 13 of the method 10, using
the known geometry between the inertial sensor unit B1 in the jig
20 and the preset virtual calibration in the inertial sensor unit
B1. The known geometry may provide a position for the mechanical
entry point via the spike 22, while the kinematics may be used to
set the mechanical axis passing through the femoral head center.
This may be done once the base 21 is driven into the femur, before
or after the steps of adjusting the orientation via the knobs 26A
and 26B.
[0060] Therefore, when the cut block 40 is assembled to the jig 20
via the connector 25A, on the bracket 25C or rails 28, the
orientation of the cut block 40 in the femoral coordinate system
(featuring the afore-mentioned landmarks) may be known as the
connection geometry between the jig 20 and the cut block 40 is
known.
[0061] Consequently, when placed on the femur, at the mechanical
axis entry point, the jig 20 may have its base 21 fixed to the
femur, and thus the inertial sensor unit B1 fixed. The abutment
plane of the jig 20, defined by the abutment surface(s) 23, may be
displaceable in two rotational DOFs relative to the base 21, via
the knobs 26A and 26B. The knob 26A may adjust a varus-valgus
orientation via a joint aligned with the anterior-posterior axis of
the femur, while the knob 26B may adjust a flexion-extension
orientation via a joint aligned with the medio-lateral axis of the
femur. When the jig 20 is abutted as desired, the bracket 25C of
the jig 20 may be in a baseline orientation, which may then be
recorded by the inertial sensor unit B2 on the cut block 40. Parts
of the jig 20 may then be removed to allow additional rotations of
the cut block 40 relative to the femur via the knobs 26A and 26B,
without having the abutment surface(s) 23 and condylar abutments 29
impeding.
[0062] When properly mounted to the distal femur, the jig 20 may
therefore have joints providing two rotational DOF about the AP
axis and the ML axis when the, and one translational DOF, in a
direction generally parallel to the AP axis. This arrangement
allows for the adjustment of the cutting block 40, as fixed to the
adjustment mechanism 25, in varus-valgus and flexion-extension. It
is also contemplated to switch the positioning of the joints
around, for instance to allow rotation about the cranial-caudal
axis.
[0063] Referring to FIGS. 6-8, the knee reference jig 30 is shown
in greater detail, and is used as an alternative to the knee
reference jig 20. However, the reference jigs 20 and 30 share
components, whereby like reference numerals will refer to like
components. The knee reference jig 30 is configured to orient
itself with the medial and lateral prominences of the epicondyles,
and is therefore used if the operator selects transepicondylar line
alignment. The jig 30 has a base 21 that defines the structure of
the jig 30, as the base 21 supports other components of the jig 30.
A pin 22 projects from the base 21, and is sized so as to be
received in a hole drilled in the distal femur at the mechanical
axis entry point. Therefore, when the pin 22 is in the drilled
hole, the jig 30 is at the mechanical axis entry point. The base 21
has an abutment plane, herein shown as a pair of abutment surfaces
23, though one or more of the abutment surfaces 23 may be present.
The abutment surfaces 23 abut against the distal surfaces of the
condyles (i.e., medial and lateral condyles) when the pin 22 is
received in the drilled hole. The base 21 also has a receptacle 24,
for receiving the inertial sensor unit B1. The receptacle 24 is
shaped for receiving the inertial sensor unit B1, such that any
preset virtual orientation or like calibration data programmed into
the inertial sensor unit B1 is aligned with physical parts of the
jig 30, such as the abutment plane and the pin 22.
[0064] An adjustment mechanism 25 is also connected to the base 21
and is also configured to support the cut block 40, with rotational
movements of the bracket 25C about pivots 25A and 25B being
controllable by the knobs 26A and 26B, respectively. The bracket
25C is therefore displaceable in two rotational DOFs relative to
the base 21, such as a rotation about the AP axis, and a rotation
about the ML axis. The knobs 26A and 26B allow minute or micro
orientation adjustments.
[0065] The jig 30 differs from the jig 20 in that the landmark
alignment unit is different. The base 21 may further define a pair
of parallel slots 27 for slidingly receiving rails 38, in a
translational DOF. An epicondylar jaw 39 is a landmark alignment
unit supported by the rails 38, such that the jaw 39 may be brought
closer or further to the base 31. The jaw 39 has bone alignment
components in the form of ends, such as pointy ends 39A, at the tip
of articulated arms 39B moving in a plane parallel to the abutment
plane of the jig 30. The ends 39A are configured to come into
contact with the prominences of the medial and lateral epicondyles,
with the ends 39A remaining collinear throughout movement of the
articular arms 39B. There is a space of gap between the ends 39A
for receiving the bone between, with a line passing through the
ends being generally parallel to the abutment plane of the abutment
surface 23. The line is used to be coincident with the
transepicondylar line or other bone landmark.
[0066] Securing the knee reference jig 30 to the distal femur
according to 11 of FIG. 1 entails inserting the pin 32 in the hole
drilled at the mechanical axis entry point, and adjusting the
penetration until the abutment plane of the base 21 is against at
least one of the distal aspects of the condyles. In an embodiment,
the jig 30 is manually oriented such that the ends 39A of the jaw
39 are aligned with the transepicondylar line from an end point of
view (i.e., located on the cranial-caudal axis). The base 21 may
then be driven into the hole of the femur 20, with the penetration
adjusted until the abutment plane of the base 21 is against at
least one of the distal aspects of the condyles. Setting the
orientation as in 12 of FIG. 1 may hence require rotating the base
21 on itself, and the jaw 39 is translated and articulated arms 39B
are displaced for the ends 39B to be aligned with the prominences
of the medial and lateral epicondyles from the cranial-caudal point
of view. The knee reference jig 30 is thus oriented with the
transepicondylar line, and may be driven into to the femur to be
fixed by way of the spike 22, though other fixation means could be
used such as pins, screws, etc, as applicable to the jig 20 as
well. The femoral coordinate system may hence be created by the
appropriate kinematics as described in 13 of the method 10, using
the inertial sensor unit B1 on the jig 30, using the known geometry
between the inertial sensor unit B1 and the preset virtual
calibration in the inertial sensor unit B1. The jaw 39 may then be
removed to navigate the orientation of the cut block 40, using the
knobs 26A and 26B.
[0067] In FIG. 7, there is also shown a front tab 31A projecting
from the base 21. The front tab 31A could be used as an alternative
to the jaw 39 to align the base 31 with Whiteside's line. The use
of the jig 30 with the tab 21A is similar to the use of the jig 30
with the jaw 39, with the base 21 being rotated on itself to align
the tab 31A with Whiteside's line, prior to being driven or secured
to the femur, via the spike 22 or equivalent fastener.
[0068] Referring to FIG. 9, the cut block 40 is shown as pinned to
the femur, after the distal cut has been performed, and thus after
14 and 15 in the method 10. The cut block 40 defines a cut slot 41
devised to receive a flat saw blade, although other configurations
are also contemplated. The cut slot 41 may therefore be aligned
with a cut plane of the cut block 40. The cut block 40 also defines
numerous guide channels for pins 42 to anchor the cut block 40 to
the distal femur once the cut block 40 is in a desired orientation,
after navigation when connected to either one of the reference jigs
20 and 30, as described above. To navigate the cut block 40
according to 14 in the method 10, the cut block 40 has a support
arm 43 with a receptacle 44 for receiving the inertial sensor unit
B2. The receptacle 44 is shaped for receiving the inertial sensor
unit B2 in a predetermined and planned arrangement, such that any
preset virtual orientation or like calibration data programmed into
the inertial sensor unit B2 is aligned with physical parts of the
cut block 40, such as the cut plane and cut slot 41. During
navigation as per 14, the cut block 40 is attached to the bracket
25C or any other component of the jig 20/30 moving relative to the
base 21, with a link (not shown) taking into account a thickness of
the implant. The adjustment mechanism 25 is at a zero setting,
i.e., a baseline setting, due to steps taken to orient the
adjustment mechanism with the landmarks of the femur, such as the
distal aspects of the condyles, and any of Whiteside's line,
posterior plane of the condyles, and/or transepicondylar axis, etc.
The knobs 26 of the jigs 20/30 are manually actuated to adjust two
rotational DOFs of the adjustment mechanism 25, resulting in
varus-valgus and/or flexion-extension adjustment for the cut plane
of the cut block 40, with reference to the baseline settings. The
cut block 40, with the concurrent readings of both inertial sensor
units B1 and B2 enabling the real-time calculation of the
orientation of the cut plane of the cut block 40 in the femoral
coordinate system. The orientation may be expressed in any
appropriate terms, such as varus-valgus, flexion-extension, etc.
Once the cut block 40 is fixed with the pins 42 to the femur in the
manner shown in FIG. 9, the knee reference jigs 20/30 may be
removed for the distal cut to be performed, as in 15 of method 10.
The inertial sensor unit B2 then becomes the unit responsible for
tracking the femoral coordinate system.
[0069] According to an embodiment, there is no inertial sensor unit
B1 on the reference jigs 20 and 30, the system using instead the
zero setting to record an orientation of the mechanical axis in the
inertial sensor unit B2, with appropriate kinematics as described
above. Then, the femur is kept in a fixed orientation while data
from the inertial sensor unit B2 during movements of the cut block
40 as connected to the adjustment mechanism 25 is used to determine
varus-valgus and flexion-extension relative to the fixed mechanical
axis.
[0070] Referring to FIGS. 10-12, the cut guide 50 is shown in a
configuration for validating the distal cut, as in 16 of the method
10. The cut guide 50 may be used with the pin A with ball head or
like bone anchor, inserted at the mechanical axis entry point,
after resection with the guiding assistance of the cut block 40.
The cut guide 50 has a base 51 that has a flat underside (a.k.a.,
sliding plane), for being laid onto the plane of the distal cut as
shown in FIG. 10. The base 51 may also have a receptacle 52. The
receptacle 52 is shaped for receiving inertial sensor unit B3 in a
predetermined and planned arrangement taking into consideration the
geometry of the cut guide 50 and the spatial relation between the
receptacle 52 and the sliding plane, such that any preset virtual
orientation or like calibration data programmed into the inertial
sensor unit B3 is aligned with physical parts of the cut guide 50,
such as the plane of the flat underside, a medio-lateral axis
and/or anterior-posterior axis of the cut guide 50, and/or a
condylar abutment plane as described hereinafter. The flat
underside may be defined by a rack 53, adapted to house the ball
head of the pin A and hence form a rotational and translational
joint. As an alternative embodiment, the ball may be on the cut
guide 50, and a socket operatively receiving the ball A may be
secured to the bone. When the flat underside of the base 51 is laid
on the distal cut plane and the base 51 is slid on the distal cut
plane--the distal cut plane and the abutment plane being
coplanar--, the cut guide 50 is constrained into moving in a single
rotational DOF, i.e., one about an axis generally parallel to the
mechanical axis. Accordingly, the combined readings of the inertial
sensor units B2 and B3 may be used by the CAS system in order to
determine the orientation of the distal cut plane relative to the
femoral coordinate system--tracked by the inertial sensor unit B2.
In an embodiment, the femur is fixed, and only the inertial sensor
unit B3 is used. In such a scenario, the inertial sensor unit B2
may be removed from the cut block 40 and be installed in the cut
guide 50, via dead reckoning.
[0071] The cut guide 50 may also be used in a navigation of the
distal cut plane as per 17 of method 10, in order to prepare
further alterations to the distal femur, as in 18 of the method 10.
The components attached to the cut guide 50 may be dependent on the
type of alignment desired by the operator. As shown in FIGS. 11 and
12, the cut guide 50 may for example have a condylar abutment 54
transversely positioned at the end of the base 51. In similar
fashion to the jig 20, the condylar abutment 54 defines a condylar
plane, configured to come into contact with posterior aspects of
the medial and lateral condyles, for posterior referencing. The
condylar plane serves as a reference plane in knee arthroplasty,
whereby the presence of the condylar abutment 54 allows alignment
of the cut guide 50 with the condylar plane, after the orientation
of the distal cut plane has been validated in the femoral
coordinate system. This may for instance be used if the reference
jig 30 was selected for alignment with the transepicondylar line.
The condylar abutment 54 may introduce a reference to the condylar
plane to the procedure. In an embodiment in which the reference jig
20 is used, the condylar abutment 54 could confirm that the
procedure up to that point is aligned with the initial alignment
using the condylar abutment 29 (FIGS. 2-5).
[0072] The joint concurrently formed by the rack 53 and the ball
head of the pin A allows movements of the cut guide 50 so that it
may come into contact with the posterior aspects of the medial and
lateral condyles. The rack 53 may also have a scale 55. The scale
55 may be used with an add-on sizing bracket 60, to determine the
size of the femoral component or implant in the anterior-posterior
direction.
[0073] Referring to FIG. 13, the cut guide 50 is shown with its
bracket 60. The bracket 60 is connected to the rack 53 to form a
translational joint having a direction parallel to the distal cut
plane when the cut guide 50 is laid onto the distal cut plane. The
bracket 60 supports a sizing boom 61 configured to be received in
the patellofemoral groove, as in FIG. 13. The bracket 60 has
pointing marks aligned with the scale 55, in order to indicate the
size of the distal cut of the femur in the anterior-posterior
direction. The measurement may be obtained when the sizing boom 61
is in the patellofemoral groove on the anterior cortex while the
condylar abutment 54 is in abutment with the posterior aspects of
the medial and lateral condyles. Drill guide holes 62 are defined
in extensions of the bracket 60. The drill guide holes 62 are
provided to place pins in the distal femur, which pins serve as
guiding landmarks for any subsequent tool to be placed against the
distal cut for the further alterations to be made to the femur, as
in 18 of the method 10.
[0074] Consequently, the reference jigs 20 and 30 physically
position and orient the method 10 with bone landmarks, and the
method 10 may then perform its subsequent steps based on the
original alignment. The cut block 40, the cut guide 50 and the
bracket 60 are positioned and orientation in continuation with the
original alignment, using appropriate sensors such as the inertial
sensor units B1, B2 and/or B3. As mentioned above, B1, B2 and B3
may be a single inertial sensor unit, moved from device to
device.
[0075] The inertial sensor units B1, B2 and B3 include one or more
inertial sensors, a transmitter (or like communication circuitry,
such as a wireless transmitter, a transceiver or the like), and may
support optional confirmation indicator or displays. If more than
one inertial sensor unit is used, the inertial sensor units
communicate with one another to share tracking data and share the
femoral coordinate system. In an embodiment of the present
disclosure, the inertial sensor may be an accelerometer providing
two rotational degrees of freedom (e.g., inertial sensor unit B3),
and may include other types of sensors, such as gyroscopes (B1).
Examples of suitable devices used as tracking circuitry 20 are the
capacitive accelerometer sensor (CAPAS), electrolytic tilt sensors
and the tri-axis sensor (TAS), amongst other possibilities. The
CAPAS provides a 2-axis measurement of the acceleration (e.g., g
force) of an object by being fixed thereto.
[0076] In the active state of the inertial sensor units B1-B3,
variations of the acceleration are reflective of a modification in
the orientation of the inertial sensor unit B1-B3. The output of
any of the inertial sensor unit B1-B3 is a 2-axis relative angular
value or 3-axis if the inertial sensor unit 12 is calibrated.
Therefore, the inertial sensor units provides real-time orientation
data for the femur.
[0077] The transmitter transmits the tracking data of the to the
processing system of the CAS system, if present, or communicates
the tracking data to the other inertial sensor units. The
transmission of data may be wireless, or through wired connection.
The technology used for the transmitter may be selected to operate
in a surgical environment, such as RF. As an example,
Bluetooth.TM., Zigbee.TM. or Wi-Fi transmitters are considered for
their wide availability and allow the integration of the trackable
member to surgical instruments. The trackable member can be
manufactured as a single disposable unit, possibly integrated to
implant instrumentation (e.g. a disposable, self-trackable cutting
guide for TKR). As an alternative embodiment, sensors can be
configured to communicate necessary information between
themselves.
[0078] Another feature considered for the inertial sensor units is
the confirmation indicator or display that provides data to the
operator or surgeon. For instance, indications about a suitable
position/orientation of the surgical tool may be provided directly
on the tool, so as to facilitate the procedure for the
surgeon/operator handling the tool. The confirmation indicator is
circuitry with on/off LEDs (e.g., red and a green LEDs) or another
suitable form of compact electronic display responsive to signals
or commands received from the CAS system.
[0079] The inertial sensor units B1, B2 and B3 are part of the CAS
system, which may or may not have a processing unit. The inertial
sensor units B1, B2 and B3 may be programmed with calibration data
(i.e., virtual preset orientation) and may have sufficient
computing capacity to perform all CAS functions described
above.
[0080] The above description makes reference to the femur. It is
however contemplated to use the reference jigs 20 and 30, the cut
block 40 and the cut guide 50 with other bones, including the
tibia, for instance to guide the resection of the tibial
plateau.
* * * * *